Process for producing interpolyesters of bibenzoic acid, and aliphatic glycol and a hetero-aliphatic glycol, and shaped articles thereof



United States Patent )fifice 3,008,931 Patented Nov. 14, 1 961 PROCESS FOR PRODUCING INTERPOLYESTERS OF BIBENZOIC ACID, AN ALIPHATIC GLYCOL AND A HETERO-ALIPHATIC GLYCOL, AND SHAPED ARTICLES THEREOF Edward A. Wielicki, Philadelphia, and Robert D. Evans,

West Chester, Pa., assignors to American Viscose Corporation, Philadelphia, Pa., a corporation of Delaware N Drawing. Filed July 28, 1958, Ser. No. 751,166 7 Claims. (Cl. 260-75) .This invention relates to new and useful interpolyesters, shaped articles prepared therefrom and methods of preparing the same. More particularly it is directed to unique interpolyesters of bibenzoic acid, an aliphatic glycol and 'a hetero-aliphatic glycol. This invention relates further to films, fibers, molded products, coatings and other shaped articles prepared from the unique interpolyesters described above.

The history of polyesters is a relatively short but active one. Condensation polyesters, while encountered in early researches such as those of Lourenco, Bischofi, Fischer, etc., were not intensively studied until 1928, when Carothers and coworkers began a systematic study of condensation polymerization. Illustrative of Carothers work is US. Patent No. 2,071,250 (1937) which discusses some of the previous work in the field and some of the problems in drawing polyesters into fibers. Carothers produced filaments from his polyesters, but they were low-melting and lacked hydrolytic stability.

The current prior art describes various linear condensation polyesters derived from dihydroxy compounds and dibasic acids, such as terephthalic acid, which are capable of being drawn into fibers showing, by characteristic X-ray patterns, orientation along the fiber axis. However, in using a single glycol and single acid to prepare a polyester, one is limited to a fixed crystal structure and melting point since the constitution of the polymer cannot be varied.

In recent years a limited amount of work has been done involving bibenzoic acid and its esters in connection with homopolyesters. The prior art indicates, however, that this work was not generally fruitful, for a homopolyester of bibenzoic acid and a glycol (e.g. polyethylenebibenzoate) possesses an extremely high melting point making its use in shaped articles entirely impractical, particularly when attempts were made to use it as a film or fiber-forming material. Moreover, and possibly more important, known polybibenzoates exhibit an extremely high rate of crystallization, making orientation of fibers or films therefrom extremely difiicult and costly, if not impossible, from a commercial standpoint.

This invention overcomes these limitations in providing as one of its objects new and useful highly polymeric interpolyesters of bibenzoic acid and a mixture of an aliphatic glycol with a hetero-aliphatic glycol having valuable properties, includingthose of being capable of being formed into useful filaments, films, and the like. It is a further object of this invention to provide unique interpolyesters as described above which possess melting interpolyesters having a low degree of solubility in ore ganic solvents. A further object is the provision of new and useful synthetic filaments and films possessing improved moisture regain characteristics. Another ob ect is the provision of new and useful synthetic fibers, film and molded objects having improved dyeing characteristics. A still further object is the provision of a new process for making the unique interpolyesters of this invention. Other objects will appear hereinafter.

The synthetic products according to the present invention are diflicultly soluble, usually crystallizable, orientable, highly polymerized interpolyesters of (1) bibenzoic acid having the general formula:

with (2) a mixture of glycols comprising (A) an aliphatic glycol having the general formula: I

wherein R is a bivalent straight or branched chain aliphatic hydrocarbon radical containing 2 to 20 carbon wherein R is a bivalent straight or branched chain aliphatic hydrocarbon radical containing 2 to 10 carbon atoms, X is an ether oxygen radical or a sulfone radical and n is an integer of from 1 to 6.

The polyesters of the present invention possess, among others, the following superior fiber and film properties: 1) controlled melting points over a relatively wide range, i.e; above 0., preferably ZOO-270 C., (2) toughness, 3) controlled crystallizability dependent upon thermal and orienting treatment, (4) orientability, (5) pliability and (6) lack of color. Items 1) and (3) are important in order that the fiber or film have good thermal and dimensional stability, as well as orientability, under a variety of conditions. The advantages of toughness, pliability and lack of color are readily apparent. In order that these latter characteristics be attained, the

fiber or film forming polymer must not crystallize too- -rapidly; otherwise it will not be possible to properly In other words, it must be capable of being orient it. easily converted to an amorphous form which can be oriented by cold or hot drawing or other known orienting procedures. On the other hand, the fiber film-forme ing polymer must have latent ability to crystallize, for if it does not it is then brittle toward impact and possesses poor dimensional stability.

In preparing the unique interpolyesters of this invention, bibenzoic acid, or a diester or acid chloride thereof,-

is reacted with the mixture of glycols described above. An ester interchange reaction is generally preferred since the time required to form the interpolyesters of this invention is generally considerably less, and/ or side-reactions can generally be minimized to a greater degree.

than when the free dicarboxylic acids are employed.

The ester interchange method for preparing the inter- 3 III. Polymerization is driven to completion by gradually reducing the pressure to remove the last traces of glycols.

The overall process is illustrated by the following equations:

wherein Y is a bivalent aliphatic hydrocarbon radical and Z is a hetero hydrocarbon radical as described in (A) and (B) above; R is a hydrocarbon radical derived from a straight or branched chain aliphatic primary or secondary monohydric alcohol boiling within the range from about 64 to 215 C. and R is hydrocarbon residue of bibenzoic acid.

In a preferred embodiment of this invention, one of the monomeric diesters of bibenzoic acid described above and a mixture of glycols (in a ratio of 90 to 10 mol percent of the aliphatic to 10 to 90 mol percent of the hetero-aliphatic) are weighed into a vessel, the ester interchange catalyst added, and a boiling chip introduced. Stage I ester interchange is then carried out at atmospheric pressure under nitrogen at a temperature between about 150 and 225 C. (preferably 175 to 200 C.) for about 2 to 10 hours, distilling off monohydric alcohol. Polymerization is then brought about in stage (II) by raising the temperature gradually to between about 200 and 400 C. (preferably about 260 to 290 C.) over a period of about /2 to 2 hours, continuing polymerization for a period of about A to 3 hours at this temperature and distilling off excess glycol. In stage (HI) pressure is gradually reduced to below about 5 mm. (preferably 0.2 to 0.5) over a period of about /2 to 4 hours (preferably about 1 to 2 hours), followed by continued heating at this elevated temperature and reduced pressure for a period of about 2 to hours. In this latter step the last traces of the glycol are distilled oif and the reaction mixture becomes progressively more viscous.

The specific temperatures and heating periods may vary over wider ranges than those outlined above depending on the observed rate of reaction. In cases where reaction becomes sluggish, higher temperature and/or longer periods of time will be employed. In those cases where the polymer is solidified, or begins to solidify before it is apparent all glycol has been removed, the temperature and/ or the heating period are increased. The conditions can be varied considerably depending upon the degree of the polyesterification desired, the ultimate properties sought, stability of the polyester being produced and use for which the product is intended. When the desired viscosity is reached under these conditions in stage .(III), evacuation and heating are discontinued, an inert gas admitted, the vessel allowed to cool to approximately room temperature and the polyester removed.

In theory a total of only one mole of the mixed glycols is necessary to efiect complete polyesterification with one mole of the monomeric diester of bibenzoic acid. However, in practice, it is diflicult to attain complete reaction under these conditions. It is therefore usually necessary to utilize an excess of the mixed glycols, preferably at least two moles thereof to one mole of the monomeric diester. Quantities, substantially larger than about 2 moles of the mixed glycols may be used; however, since they are not necessary, in the interests of economy, they are not recommended.

Examples of some of the various monomeric diesters which can be employed in accordance with the process of the invention include those derived from bibenzoic acid and one of the following primary monohydric alcohols: methanol, ethanol, propanol-l, 2-methyl-propanol-l, butanol-l, 2-methyl-butanol-4, 2,2-dimethyl propanol-l, pentanol-l, 2-methyl-pentanol-1, 2-methyl-pentanol-S, 3-methylol-pentane, hexanol-l, Z-methyI-hexanol-l, 2-methyl-hexanol-6, heptanol-l, 2-ethyl-hexanol-1, octanol-l, nonanol-l, 2,6-dimethyl-3-rnethylol heptane. Diesters derived from bibenzoic acid and secondary monohydric alcohols can be utilized also, e.g. propanol-Z, butanol-2, 2-methyl-butanol-3, pentanol-Z, pentanol-3, 2- methyl-pentanol-3, 3-methyl-pentanol-2, hexanol-Z, 2,2- dimethyl-butanol-3, 2-methyl hexanol-3, heptanol-4, octanol-2, decanol-4.

Since in the preferred process, the alcohols from which the diesters are derived are removed from the reaction zone by boiling, it is generally necessary to utilize a glycol having a boiling point higher than that of the alcohol being evolved. Examples of some of the glycols described in (A) and (B) above are as follows:

(A) Ethylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, decamethylene glycols, 2,2- dimethyl-l,3-propane-diol, 2,2,3,3-tetramethyl 1,4,-butanediol, 2-buten-1,4-diol, 2-heXen 1,6-diol, 3octen-1,8- diol, 2-penten-1,4-diol, 3-hepten-1,5-diol, etc.

(B) Diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, 4,4'-dihydroxy-dibutyl-ether, other polyoxyalkylene glycols having 1 to 6 oxyalkylene units wherein said oxyalkylene unit contains 1 to 10 carbon atoms, 2,2-sulfonyl-diethanol, 4,4'-sulfonyl-dibuta- 1101, 3,3 [sulfonyl bis (3 propyl sulfonyl)] di- P PE L [1,4 butylene disulfonyl bis (4-butyl-sulfonyl) ]-dib-utanol, sulfonyl-bis- (4 butyl-sulfonyl-4- butyl-sulfonyl-4-butanol) 6,6-( 1,6-hexylene-disulfonyl)- dihexanol, sulfonyl-bis- [3 2,2-dimethyl) -propanol] 1,3-

(2,2-dimethyl)propylene-disulfonyl-bis-[3 (2,2-dimethyl) -propyl-sulfonyl-3- 2,2-dimethyl) -propanol] sulfonylbis- [4- (2,2,3,3-tetramethyl) butanol] The properties of films, fibers, or other molded objects which constitute a preferred embodiment of this invention may vary greatly depending in a large measure upon the quantity, and to a lesser degree the identity, of the glycol utilized to form the inter'polyester. Thus melting points, degree of crystallinity, rate of crystallizing, etc. may vary considerably.

The catalytic condensing agents or ester-interchange catalyst which may be employed are conventional ones and include, for example, the alkali metals, the alkaline earth metals; the oxides, carbonates, and borates of these two groups of metals, the one to six carbon alkoxides of these two groups of metals; magnesium, zinc, and manganese; the oxides of these metals; zinc borate; the sulfates, phosphates and acetates of zinc, cadmium, mag-i nesium aluminum and copper; litharge or a combination of litharge with antimony trioxide and triphenyl phosphite as described in U.S. Patent No. 2,650,213; compounds of the formula:

' From about 0.005% to about 0.2% of such catalysts based on the weight of diester monomer being condensed may be employed. Higher or lower percentages may also be employed. Generally, from about 0.01% to about 0.05% of the catalytic condensing agent can be advantageously employed, based on the weight of dibasic acid diester being condensed. As will be apparent to those skilled in the art, it is generally advantageous from a cost standpoint to utilize the minimum quantity of one of the above catalysts which elfect optimum results. Obviously, however, quantities larger or smaller than those outlined above will be employed by those skilled in the art where needed, e.g. to accelerate or decelerate rate of reaction, to modify propertiesluster, molecular weight, tenacity, etc.

The reaction can be carried out in the presence or absence of a solvent, preferably the latter. Illustrative of such solvents are inert high boiling compounds, such as diphenyl ether, diphenyl, mixed tolyl sulfones, chlorinated naphthalene, chlorinated diphenyl, dimethyl sulfolane, etc.

It is essential to exclude oxygen and moisture at all stages of the condensation reaction. Otherwise discoloration, low molecular weight, and/or insolubilization of the polyester results. Inert atmospheres which can advantageously be employed include nitrogen, hydrogen, helium, etc. The exclusion of moisture is readily effected by employing substantially anhydrous reactants.

The interpolyesters of this invention can be formed into filaments or films by conventional melt extrusion procedures. For example, the interpolyesters can be melt extruded vertically at a melt temperature of approximately 25 C. above the melting point of the interpolyester followed by immediate quenching and subsequently orientating.

Although illustrated in the preferred embodiment as a batch process, the interpolyesters of this invention can be produced by continuous methods also; for example, the required amounts of the several reactants and catalyst can be continuously metered into the reaction vessel, maintained therein for the required reaction time under the required reaction conditions of temperature and pressure and then continuously drawn off.

The following examples are not given by way of limitation, the scope of the invention being determined by the appended claims. In all of the following examples, PbO is litharge.

Example 1.Polyethylene/diethylene bibenzate1 0/ 90 mol percent A polymerization vessel fitted with an exit tube, water cooled condenser and a water cooled receiver was charged with 14.92 grams (0.05 mole) diethyl bibenzoate, 10.51 grams (0.099 ,mole) diethylene glycol and 0.683 g. (0.011 mole) ethylene glycol. To this. mixture were added 0.005 g. PbO and 0.005 g. cobaltous acetate as a mixed catalyst for ester interchange and a boiling chip to prevent bumping during subsequent heating. The polymerization vessel was evacuated and flushed with oxygen-free nitrogen 3 times prior to heating, then heated rapidly to 190 C. during which time the reactants melted with rapid evolution of ethanol. The initial ester interchange to produce the mixed glycol esters was carried out at 190 C. for 4 hours to assure complete conversion to the desired products resulting in thin mobile clear liquids which on cooling solidified to white opaque solids.

The vessel was gradually heated to 275 C. over a 1 hour period with distillation of glycols. The polymerization temperature was maintained at 275 C. while the pressure was gradually reduced over a 1 hour period to' less than 1 mm. and polymerization continued under these conditions for an additional 5 hours. The polymer thus produced was a viscous pale colored liquid which crystallized to a white opaque hard solid on cooling.

6 The polymer had a birefringent melting point of 169 C. and formed fibers and translucent flexible films.

Example 2.-Polyethylene/a'iethylene bibenz0ate-20/ mol percent A polymerization vessel fitted with an exit tube, water cooled condenser and a water cooled receiver was charged with 14.92 grams (0.05 mole) diethyl bibenzoate, 9.34 grams (0.088 mole) diethylene glycol and 1.37 g. (0.022 mole) ethylene glycol. To this mixture were added 0.005 g. PbO and 0.005 g. cobaltous acetate as a mixed catalyst for ester interchange and a boiling chip to prevent bumping during subsequent heating. The polymerization vessel was evacuated and flushed With oxygen-free nitrogen 3 times prior to heating, then heated rapidly to C. during which time the reactants melted with rapid evolution of ethanol. The initial ester interchange to produce the mixed glycol esters was carried out at 190 C. for 4 hours to assure complete conversion to the desired products resulting in thin mobile clear liquids which on cooling solidified to white opaque solids. The vessel was gradually heated to 275 C. over a 1 hour period with distillation of glycols. The polymerization temperature was maintained at 275 C. while the pressure was gradually reduced over a 1 hour period to less than 1 mm. and polymerization continued under these conditions for an additional 5 hours. The polymer thus produced was a viscous pale colored liquid which crystallized to a white opaque solid on cooling. The polymer had a birefringent melting point of 164 C. and formed fibers and translucent flexible films.

Example 3.P0lyethylene/diethylene bibenz0ate30/ 70 mol percent A. polymerization vessel fitted with an exit tube, water cooled condenser and a water cooled receiver was charged with 14.92 grams (0.05 mole) diethyl bibenzoate, 8.17 grams (0.077 mole) diethylene glycol and 2.05 g. (0.033 mole) ethylene glycol. To this mixture were added 0.005 g. PbO and 0.005 g. cobaltous acetate as a mixed catalyst for ester interchange and a boiling chip to prevent bumping during subsequent heating. The polymerization vessel was evacuated and flushed with oxygen-free nitrogen 3 times prior to heating, then heated rapidly to 190 C. during which time the reactants melted with rapid evolution of ethanol. The initial ester interchange to produce the mixed glycol esters was carried out at 190 C. for 4 hours to assure complete conversion to the desired products resulting in thin mobile clear liquids which on cooling solidified to white opaque solids. The vessel was gradually heated to 275 C. over a 1 hour period with distillation of glycols. The polymerization temperature was maintained at 275 C. while the pressure was gradually reduced over a 1 hour period to less than 1 mm. and polymerization continued under these conditions for an additional 5 hours. The polymer thus pro duced was a viscous pale colored liquid which crystallized to a white opaque solid on cooling. The polymer had a birefringent melting point of 171 C. and formed fibers and translucent flexible films.

Example 4.--P0lyelhylene/diethylene bibenzoate- 40/60 mol percent A polymerization vessel fitted with an exit tube, water cooled condenser and a water cooled receiver was charged with 14.92 grams (0.05 mole) diethyl bibenzoate, 7.0 grams (0.066 mole) diethylene glycol and 2.73 g. (0.044 mole) ethylene glycol. To this mixture were added 0.005 g. PbO and 0.005 g. cobaltous acetate as a mixed catalyst for ester interchange and a boiling chip to prevent bumping during subsequent heating. The polymerization vessel was evacuated and flushed with oxygenfree nitrogen 3 times prior to heating, then heated rapidly to 190 C. during which time the reactants melted'with rapid evolution of ethanol. The initial ester interchange 5 to produce the mixed glycol esters was carried out at 190 which on cooling solidified to white opaque solids.

C. for 4 hours to assure complete conversion to the desired products resulting in thin mobile clear liquids which on cooling solidified to white opaque solids. The vessel was gradually heated to 275 C. over a 1 hour period with distillation of glycols. The polymerization temperature was maintained at 275 C. while the pressure was gradually reduced over a 1 hour period to less than 1 mm. and polymerization continued under these conditions for an additional 5 hours. The polymer thus produced was a viscous pale colored liquid which crystallized to a white opaque solid on cooling. The polymer had a birefringent melting point of 169 C. and formed fibers and translucent flexible films.

Example 5.-Plyethylene/diethylene bibenzoate- 50/50 mol percent A polymerization vessel fitted with an exit tube, water cooled condenser and a water cooled receiver was charged with 14.92 grams (0.05 mole) diethyl bibenzoate, 5.84 grams (0.055 mole) diethylene glycol and 3.41 g. (0.055 mole) ethylene glycol. To this mixture were added 0.005 g. PbO and 0.005 g. cobaltous acetate as a mixed catalyst for ester interchange and a boiling chip to prevent bumping during subsequent heating. The polymerization vessel was evacuated and flushed with oxygen-free nitrogen 3 times prior to heating, then heated rapidly to 190 C. during which time the reactants melted with rapid evolution of ethanol. The initial ester interchange to produce the mixed glycol esters was carried out at 190 C. for 4 hours to assure compelte conversion to the desired products resulting in thin mobile clear liquids which on cooling solidified to white opaque solids. The vessel was gradually heated to 275 C. over a 1 hour period with distillation of glycols. The polymerization temperature was maintained at 275 C. while the pressure was gradually reduced over a 1 hour period to less than 1 mm. and polymerization continued under these conditions for an additional hours. The polymer thus produced was a very viscous pale colored liquid which crystallized to a white opaque solid on cooling. The polymer had a birefringent melting point of 177 C. and formed fibers and translucent flexible films.

Example 6.P0lyethylene/diethylene bibenz0ate- 60/40 mol percent A polymerization vessel fitted with an exit tube, water cooled condenser and a water cooled receiver was charged with 14.92 grams (0.05 mole) diethyl bibenzoate, 4.67 grams (0.044 mole) diethylene glycol and 4.10 g. (0.066 mole) ethylene glycol. To this mixture were added 0.005 g. PbO and 0.005 g. cobaltous acetate as a mixed catalyst for ester interchange and a boiling chip to prevent bumping during subsequent heating. The polymerization vessel was evacuated and flushed with oxygenfree nitrogen 3 times prior to heating, then heated rapidly to 190 C. during which time the reactants melted with rapid evolution of ethanol. The initial ester interchange to produce the mixed glycol esters was carried out at 190 C. for 4 hours to assure complete conversion to the desired products resulting in thin mobile clear liquids The vessel was gradually heated to 275 C. over a 1 hour period with distillation of glycols. The polymerization temperature was maintained at 275 C. while the pressure was gradually reduced over a 1 hour period to less than 1 mm. and. polymerization continued under these conditions for an additional 5 hours. The polymer thus produced was a very viscous pale colored liquid which crystallized to a white opaque solid on cooling. The polymer had a birefringent melting point of 189 C. and formed fibers and translucent flexible films.

A polymerization vessel fitted with an exit tube, water cooled condenser and a water cooled receiver was charged with 14.92 grams (0.05 mole) diethyl bibenzoate, 3.50 grams (0.033 mole) diethylene glycol and 4.78 g. (0.077 mole) ethylene glycol. To this mixture were added 0.005 g. PhD and 0.005 g. cobaltous acetate as a mixed catalyst for ester interchange and a boiling chip to prevent bumping during subsequent heating. The polymerization vessel was evacuated and flushed with oxygen-free nitrogen 3 times prior to heating, then heated rapidly to 190 C. during which time the reactants melted with rapid evolution of ethanol. The initial ester interchange to produce the mixed glycol esters was carried out at 190 C. for 4 hours to assure complete conversion to the desired products resulting in thin mobile clear liquids which on cooling solidified to white opaque solids. The vessel was gradually heated to 275 C. over a 1 hour period with distillation of glycols. The polymerization temperature was maintained at 275 C. while the pressure was gradually reduced over a 1 hour period to less than 1 mm. and polymerization continued under these conditions for an additional 5 hours. The polymer thus produced was a viscous pale colored liquid which crystallizedto a white opaque solid on cooling. The polymer had a birefringent melting point of 213 C. and formed fibers and translucent flexible films.

Example 8.-P0lyethylene/diethylene bibenzoate- /20 mol percent A polymerization vessel fitted with an exit tube, water cooled condenser and a water cooled receiver was charged with 14.92 grams (0.05 mole) diethyl bibenzoate, 2.33 grams (0.022 mole) diethylene glycol and 5.46 g. (0.088 mole) ethylene glycol. To this mixture were added 0.005 g. PbO and 0.005 g. cobaltous acetate as a mixed catalyst for ester interchange and a boiling chip to prevent bumping during subsequent heating. The polymerization vessel was evacuated and flushed with oxygenfree nitrogen 3 times prior to heating, then heated rapidly to 190 C. during which time the reactants melted with rapid evolution of ethanol. The initial ester interchange to produce the mixed glycol esters was carried out at 190 C. for 4 hours to assure complete conversion to the desired products resulting in thin mobile clear liquids which on cooling solidified to white opaque solids. The vessel was gradually heated to 275 C. over a 1 hour period with distillation of glycols. The polymerization temperature was maintained at 275 C. while the pressure was gradually reduced over a 1 hour period to less than 1 mm. and polymerization continued under these conditions for an additional 5 hours. The polymer thus produced was a viscous pale colored liquid which crystallized to a white opaque solid on cooling. The polymer had a birefringent melting point of 268 C. and formed fibers and translucent flexible films.

Example 9.P0lyethylene/diethylene bibenz0ate- /10 mol percent A polymerization vessel fitted with an exit tube, water cooled condenser and a water cooled receiver was charged with 14.92 grams (0.05 mole) diethyl bibenzoate, 1.17 grams (0.011 mole) diethylene glycol and 6.14 g. (0.099 mole) ethylene glycol. To this mixture were added 0.005 g. PbO and 0.005 g. cobaltous acetate as a mixed catalyst for ester interchange and a boiling chip to prevent bumping during subsequent heating. The polymerization vessel was evacuated and flushed with oxygen-free nitrogen 3 times prior to heating, then heated rapidly to C. during which time the reactants melted with rapid evolution of ethanol. The initial ester interchange to produce the mixed glycol esters was carried out at 190 C. for 4 hours to assure complete conversion to the desired products resulting in thin mobile clear liquids which on cooling solidified to white opaque solids. The vessel was gradually heated to 275 C. over a 1 hour period with distillation of glycols. The polymerization temperature was maintained at 275 C. while the pressure was gradually reduced over a 1 hour period to less than 1 mm. and polymerization continued under these conditions for an additional 5 hours. The polymer thus produced was a white opaque solid on cooling having a birefringent melting point of 327 C.

Example A polymerization vesselfitted with an exit tube, water cooled condenser and a water cooled receiver was charged with 17.90 grams (0.06 mole) diethyl bibenzoate, 1.35 grams (0.013 mole) neopentylene glycol and 12.62 g. (0.119 mole) diethylene glycol. To this mixture were added 0.01 g. zinc acetate, 0.01 g. manganous acetate and 0.005 g. lithium hydride as a mixed catalyst for ester interchange and a boiling chip to prevent bumping during subsequent heating. The polymerization vessel was evacuated and flushed with oxygen-free nitrogen 3 times prior to heating, then heated rapidly to 190 C. during which time the reactants melted with rapid evolution of ethanol. The initial ester interchange to produce the mixed glycol esters was carried out at 190 C. for 5 hours to assure complete conversion to the desired products resulting in thin mobile clear liquids which on cooling solidified to white pasty solids. The vessel was gradually heated to 270 C. over a 1 hour period. The polymerization temperature was maintained at 270 C. while the pressure was gradually reduced over a 1 hour period to less than 1 mm. and polymerization continued under these conditions for an additional 4.5 hours. The polymer thus produced was a viscous straw colored liquid which crystallized to a butt opaque solid on cooling. The polymer had a birefringent melting point of 184 C. and formed fibers and transparent films.

Example 11 A polymerization vessel fitted with an exit tube, water cooled condenser and a water cooled receiver was charged with 17.90 grams (0.06 mole) diethyl bibenzoate, 5.52 grams (0.053 mole) neopentylene glycol and 8.38 g. (0.079 mole) diethylene glycol. To this mixture were added 0.01 g. zinc acetate, 0.01 g. manganous acetate and 0.005 g. lithium hydride as a mixed catalyst for ester interchange and a boiling chip to prevent bumping during subsequent heating. The polymerization vessel was evacuated and flushed with oxygen-free nitrogen 3 times prior to heating, then heated rapidly .to 190 C. during which time the reactants melted with rapid evolution of ethanol. The initial ester interchange to produce the mixed glycol esters was carried out at 190 C. for 5 hours to assure complete conversion to the desired products resulting in thin mobile clear liquids which on cooling solidified to white opaque solids. The vessel was gradually heated to 270 C. over a 1 hour period. The polymerization temperature was maintained at 270 C. while the pressure was gradually reduced over a 1 hour period .to less than 1 mm. and polymerization continued under these conditions for an additional 4.5 hours. The polymer thus produced was a viscous straw colored liquid which crystallized to a bull opaque solid on cooling. The polymer had a birefringent melting point of 138 C. and formed fibers and transparent films.

Exdmple 12 A polymerization vessel fitted with an exit tube, water cooled condenser and a water cooled receiver was charged with 17.90 grams (0.06 mole) diethyl bibenzoate, 2.71 grams (0.026 mole) neopentylene glycol and 15.92 g. (0.106 mole) triethylene glycol. To this mixture were added 0.01 g. zinc acetate, 0.01 g. manganous acetate and 0.005 g. lithium hydride as a mixed catalyst for ester interchange and a boiling chip to prevent bumping during subsequent heating. The polymerization vessel was evacuated and flushed with oxygen-free nitrogen 3 times prior to heating, then heated rapidly to 190 C. during which time the reactants melted with rapid evolution of ethanol. The

10 initial ester interchange to produce the mixed glycol esters was carried out at 190 C. for 5 hours to assure complete conversion to the desired products resulting in thin mobile clear liquids which on cooling solidified to white opaque pasty solids. The vessel was gradually heated to 270 C. over a 1 hour period. The polymerization temperature was maintained at 270 C. while the pressure was gradually reduced over a 1 hour period to less than 1 mm. and polymerization continued under these conditions for an additional 4.5 hours. The polymer thus produced was a viscous straw colored liquid which crystallized to a light tan opaque solid on cooling. The polymer had a birefringent melting point of 88 C. and formed fibers and transparent films.

Example 13 A polymerization vessel fitted with an exit tube, water cooled condenser and a water cooled receiver was charged with 17.90 grams (0.06 mole) diethyl bi benzoate, 6.87

grams (0.066 mole) neopentyl glycol and 9.91 g. (0.066

mole) triethylene glycol. To this mixture were added 0.01 g. zinc acetate, 0.01 g. manganous acetate and 0.005 g. lithium hydride as a mixed catalyst for ester interchange and a boiling chip .to prevent bumping during subsequent heating. The polymerization vessel was evacuated and flushed with oxygen-free nitrogen 3 times prior to heating, then heated rapidly to 190 C. during which time the reactants melted with rapid evolution of ethanol. The initial ester interchange to produce the mixed glycol esters was carried out at 190 C. for 5 hours to assure complete conversion to the desired products resulting in thin mobile clear liquids which on cooling solidified to white opaque solids. The vessel was gradually heated to 270 C. over a 1 hour period. The polymerization temperature was maintained at 270 C. while the pressure was gradually reduced over a 1 hour period to less than 1 mm. and polymerization continued under these conditions for an additional 4.5 hours. The polymer thus produced was a viscous brown colored liquid which crystallized to an amber transparent solid on cooling. The polymer had a softening point of 82 C. and formed fibers and transparent films.

We claim:

1. A filament and filmforming linear interpolyester melting above 140 C. of components consisting essentially of p, p bibenzoic acid and at least two mols of mixed glycols per mol of said acid, said mixed glycols consisting essentially of from 10 to mol percent of an aliphatic glycol having the general formula HO--R--'OH wherein R is a bivalent aliphatic hydrocarbon radical having from 2 to 20 carbon atoms and from 90 to 20 mol percent of a hetero-aliphatic glycol having the following general formula:

wherein R is a bivalent aliphatic hydrocarbon radical containing from 2 to 10 carbon atoms and n is an integer of from 1 to 6, said interpolyesters melting above C.

2. The linear interpolyester of claim l melting between 200 and 270 C.

3. The linear interpolyester of claim 2 wherein the mixed glycols consist essentially of ethylene glycol as the aliphatic glycol and diethylene glycol as the hetero-aliphatic glycol.

4. The linear interpolyester of claim 2 wherein the mixed glycols consist essentially of neopenty lene glycol as the aliphatic glycol and diethylene glycol as the hetero-aliphatic glycol.

5. The process of preparing filament and film-forming linear interpolyesters melting above 140 C. comprising reacting components consisting essentially of a lower alkyl diester of bibenzoic acid and at least two mols of mixed glycols per mol of said diester, said mixed glycols consisting essentially of from 10 to 80 mol percent of an aliphatic glycol having the general formula HOROH wherein R is a bivalent aliphatic hydrocarbon radical having from 2 to 20 carbon atoms and from 90 to 20 mol percent of a hetero-aliphatic glycol having the following general forwherein R is a bivalent aliphatic hydrocarbon radical containing 2 to 10 carbon atoms and n is an integer of from 1 to 6, reacting said components at a temperature above 150 C. in the presence of an ester interchange catalyst and in the absence of oxygen and moisture.

6. The process of claim 5 wherein the initial reaction temperature is kept from 150 to 200 C. until no further alcohol is liberated and thereafter the temperature is raised to from 200 to 400 C. With a gradual reduction of reaction pressure to less than 5 mm. of mercury.

References Cited in the file of this patent UNITED STATES PATENTS 2,437,046 2,727,881 Caldwell et a1. Dec. 20, 1955 2,799,667

Drewitt et al July 16, 1957 OTHER REFERENCES Page 331, Bennett, Concise Chemical and Technical Dictionary, published 1957, Chemical Publishing Co., Inc.,

7. The process of claim 6 wherein the initial temperature 15 Brooklyn, New York- Rothrock et 'al Mar. 3, 1948 

1. A FILAMENT AND FILM-FORMING LINEAR INTERPOLYESTER MELTING ABOVE 140*C. OF COMPONENTS CONSISTING ESSENTIALLY OF P,P'' BIBENZOIC ACID AND AT LEAST TWO MOLS OF MIXED GLYCOLS PER MOL OF SAID ACID, SAID MIXED GLYCOLS CONSISTING ESSENTIALLY OF FROM 10 TO 80 MOL PERCENT OF AN ALIPHATIC GLYCOL HAVING THE GENERAL FORMULA HO-R-OH WHEREIN R IS A BIVALENT ALIPHATIC HYDROCARBON RADICAL HAVING FROM 2 TO 20 CARBON ATOMS AND FROM 90 TO 20 MOL PERCENT OF A HETERO-ALIPHATIC GLYCOL HAVING THE FOLLOWING GENERAL FORMULA: 